Sleep duration and mortality among breast cancer survivors in the Western New York Exposures and Breast Cancer (WEB) Study

Purpose: There is increasing evidence that sleep duration may affect breast cancer survival through effects on circadian function, influencing disease progression. However, further investigation of this association is needed. Methods: In a population-based, prospective cohort study of women from the Western New York Exposures and Breast Cancer Study, we examined mortality outcomes with invasive breast cancer identified using the National Death Index. Cox proportion hazards ratios with 95% confidence intervals were used to estimate risk of all-cause (AC) and breast cancer-specific (BC) mortality associated with self-reported usual sleep duration with adjustment for age, race/ethnicity, years of education, body mass index (BMI), menopausal status, pack-years of smoking, tumor stage, and estrogen-receptor (ER) status. We further examined associations within strata of BMI, tumor stage, menopausal status, and ER status. Results: A sample of 817 patients with breast cancer were followed for a median of 18.7 years, during which 339 deaths were reported, including 132 breast cancer-specific deaths. Those who reported shorter or longer sleep tended to have a slightly higher BMI, to be less proportionately non-Hispanic White, to report a previous history of benign breast disease, and to have consumed more alcohol during their lifetime. We found no significant associations between sleep duration and AC or BC mortality, including within stratified analyses. Conclusion: Sleep duration was not associated with either AC or BC mortality including within strata of BMI, tumor stage, menopausal status, or ER status.